The present invention relates to an ocean bottom sampling device, and more particularly, to a device having two sets of wheels which allow it to travel over rough terrain while still maintaining the sampler's net opening near the ocean floor.
In both environmental impact studies and marine biological research programs, it is very often necessary to determine the abundance and distribution of fish life at various depths along the water column of the ocean. Typically, this information is obtained by passing a net through a known volume of water and then counting the number of fish trapped within the net. The net and the device to which it is attached is often called a "sampler". The volume of water sampled is ordinarily determined by multiplying the cross-sectional area of the net opening by the distance through which the net has been passed. The present invention focuses on the problem of measuring fish life which inhabits the water very close to the ocean floor.
In the past, this problem has been primarily approached through the use of sled-like samplers. These sleds typically had elongate, rigid bodies which were essentially rectangular in shape, and had a conical-shaped net attached at the rear. A tow rope was attached to the sled enabling it to be dragged along the ocean bottom behind a boat. The primary advantage of using these sleds to sample the ocean bottom was that the rigidity of their bodies ensured that the net opening would always remain perpendicular to the ocean floor. Thus, the cross-sectional area of the net opening was a constant, thus making accurate water volume measurements possible.
However, there were several disadvantages to the use of these sleds. First, the framework of the sled and the attached tow rope often obstructed the opening of the net, thereby causing many fish to avoid entering the net and resulting in inaccurate measurements. This was especially true with respect to larval and juvenile fishes, the abundance and distribution of which are of particular importance in environmental impact studies.
Secondly, the sleds often became snagged or damaged by contact with rocks or other obstructions on the ocean floor. This problem often resulted in inaccurate samples, or required that the measurements be repeated. Also, the sleds often had to be repaired or replaced.
Thirdly, and most significantly, because of the long rigid nature of the prior art sleds, they did not perform well in hilly terrain. That is, the sleds would often pass from peak-to-peak without sampling the fish found in the valleys. As mentioned above, it is very important to sample fish life very close to the bottom, for example, within 5 or 6 inches of the ocean floor. Thus, the failure of these prior art sleds to sample the fish in the valleys between peaks led to inaccurate measurements.
The ocean bottom sampler of the present invention solves the problems presented by the prior art by the novel use of a wheeled sampler. The present invention also maintains the net opening in a vertical position and close to the ocean floor.